How to Make It
Tear the ancho chiles into flat pieces, then toast a few at a time in a dry skillet over medium heat: flatten with a metal spatula for a few seconds, until they crackle and change color slightly, then flip and press again. (If they give off more than the slightest wisp of smoke, they are burning and will add a bitter element to the sauce.) In a small bowl, soak the chiles in hot water for 30 minutes, stirring occasionally. Drain and discard the water.
Heat 1 tablespoon of the oil in a heavy, medium (4-quart) pot (preferably a Dutch oven) over medium heat. Add the onion and garlic cloves, and cook, stirring regularly, until well browned, about 10 minutes. Scrape into a blender jar. Set the pan aside.
Preheat the broiler. Broil the tomatoes on a baking sheet 4-inches from the heat source until blackened, about 5 minutes, then flip and repeat on the other side. Let cool, then peel, collecting all the juices from the tomato. Add the tomato to the blender, along with 1 cup of the peanuts, the bread, chipotles, drained anchos, allspice and cinnamon. Add 1 1/2 cups of the broth and blend until smooth, stirring and scraping down the sides of the blender jar; add more liquid if needed. Press the mixture through a medium-mesh strainer set over a bowl.
Heat 1 tablespoon of the remaining oil in the pot over medium high, until shimmering. Add the puree all at once. Stir as the nutty-smelling mixture thickens and darkens for about 5 minutes, then stir in the remaining 2 cups broth, the wine, vinegar and bay leaves. Partially cover and let gently simmer over medium-low heat for roughly 45 minutes, stirring regularly for the flavors to harmonize. If necessary, thin the sauce with a little more broth to keep it the consistency of a cream soup. Taste and season with salt, usually about 1 1/2 teaspoons, and the sugar. Cover and keep warm.
Forty-five to 60 minutes before serving, heat a gas grill to medium-high or light a charcoal fire and let it burn just until the coals are covered with gray ash and very hot. Set the fire up for indirect grilling: turn the gas burner(s) in the center of the grill off or bank the coals to the sides of the grill. Set the cooking grate in place, cover the grill and let the grate heat up, 5 minutes or so.
While the grill heats, brush the pork loin with some of the remaining 2 tablespoons of oil; sprinkle with salt and pepper.
Lay the pork in the center of the grill (not over direct heat). Cover and cook about 25 to 35 minutes, until the center of the pork registers 145° on an instant-read thermometer. The meat will feel rather firm (not hard) to the touch and cutting into the center will reveal only the slightest hint of pink.
Transfer to a cutting board. Tent with foil and let rest for 5 minutes. Then cut into thin slices. Ladle a generous 1/3 cup of the mole sauce onto each of 6 warm dinner plates. Set 2 or 3 pork slices over the sauce. Garnish with chopped peanuts and sprigs of parsley.